Abstract [en]

The objective of the study was to describe prevalence of overweight, obesity, and underweight among 10-11 year old children during a four year period. This was done by comparing 1989 and 1993 birth cohorts, with focus on gender and socioeconomic (SES) using data from small geographical areas. The study was performed 2005 in Stockholm county where SES areas and schools within SES areas were randomly sampled. In selected schools, anthropometric data from routine assessments of 4thgraders were abstracted from school records. Weights, heights and birthdates were retrieved from 2416 10-11 year olds born in 1989 and 2183 born in 1993. Overweight and obesity were defined according to Cole’s age- and sex-specific BMI cut-off points. Underweight was defined as -2 SD according to the national growth reference curves established by Karlberg and coworkers 2001. Secular trends in prevalence between 1989 and 1993 seemed to vary by sex. In boys, the prevalence of overweight was 21.3 % in both birth cohorts, while obesity increased non-significantly from 3.1 to 4.0 %. In girls overweight decreased non-significantly from 22.9 to 19.7 and obesity decreased from 4.6 to 2.9 % (RR= 0.62 95 % CI: 0.41-0.98). The prevalence of underweight decreased non-significantly both in boys and in girls. When comparing the different SES-areas the social gradient was more obvious in birth cohort 1993 than cohort 1989. In birth cohort 1993 17.1 % of the boys were overweight in the most affluent area compared to 29.0 % in the low SES area. For obesity the prevalences were 1.9 % and 6.0 % respectively. In girls there is a slightly different pattern; among girls in the low SES areas the prevalence of overweight are almost identical 28.4 and 28.3. In the other areas the 1993 cohort shows a lower overweight prevalence compared to girls born 1989. In summary decreases in obesity occurred in girls from the two respective birth cohorts; at the same time both overweight and underweight tended to decrease. In contrast, among boys, there were no significant differences over time, although increases in obesity were detected among boys in less advantaged socioeconomic areas.This underlines the need for computer based monitoring of routine height and weight measurements in schools and preventive efforts which target children and their families in areas of low-socioeconomic status in early childhood.